Molding method

ABSTRACT

A cycle is repeatedly carried out, the cycle including: a material feeding step of feeding a material whose amount is larger than an amount that is needed to form a single mold; a mixing step; an ejection step; and a measurement step of measuring, once before or after the ejection step, an amount of foamed mixed sand contained in a mixing tank. The material at least partially is not fed in the material feeding step in the cycle in which the amount of the foamed mixed sand is not less than a first threshold.

This Nonprovisional application claims priority under 35 U.S.C. § 119 on Patent Application No. 2020-049923 filed in Japan on Mar. 19, 2020, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a molding method for forming a mold.

BACKGROUND ART

A mold (in particular, a core) is formed by feeding a material into a mixing tank, mixing the material in the mixing tank so as to obtain foamed mixed sand, and ejecting the foamed mixed sand via an ejection port of the mixing tank so as to inject the foamed mixed sand into a mold.

Examples of a method for ejecting foamed mixed sand include (i) a method for ejecting foamed mixed sand by pressing the foamed mixed sand by a piston and (ii) a method for ejecting foamed mixed sand by pressing the foamed mixed sand by compressed air instead of a piston.

For example, Patent Literature 1 discloses a technique in which a material is fed from a material feeding device into a mixing tank so that foamed mixed sand obtained by mixing the material in the mixing tank is ejected by a force of air.

CITATION LIST Patent Literature [Patent Literature 1]

-   Japanese Patent Application Publication Tokukai No. 2018-192512     (Publication date: Dec. 6, 2018)

SUMMARY OF INVENTION Technical Problem

Assume here that foamed mixed sand is ejected by pressing the foamed mixed sand by a piston. In this case, an amount of a material which amount is necessary for subsequent ejection of the foamed mixed sand is determined from a location of the piston by which to eject the foamed mixed sand contained in the mixing tank.

In contrast, in a case where foamed mixed sand is ejected by pressing the foamed mixed sand by air, no piston is used. This prevents an amount of a material which amount is necessary for subsequent ejection of the foamed mixed sand from being determined by such a method as described earlier. Thus, conventionally, a load cell or a level sensor is used to measure an amount of foamed mixed sand, contained in a mixing tank, before and after ejection of the foamed mixed sand, and a material is fed into the mixing tank in an amount as large as the amount of the foamed mixed sand ejected.

However, according to such a conventional technique, an amount of foamed mixed sand is measured twice while a single cycle consisting of a process for forming a mold is carried out. This makes longer a cycle time that it takes to carry out a single cycle consisting of the above process.

An aspect of the present invention has been made to solve the problems described earlier. An object of an aspect of the present invention is to achieve (i) a molding method that makes it possible to reduce a cycle time that it takes to carry out a single cycle consisting of a process for forming a mold and (ii) a technique related to the molding method.

Solution to Problem

In order to attain the object, a molding method in accordance with an aspect of the present invention includes: repeatedly carrying out a cycle, the cycle including: a material feeding step of feeding, into a mixing tank, a material whose amount is larger than an amount that is needed to form a single mold; a mixing step of mixing the material, contained in the mixing tank, so as to produce foamed mixed sand; an ejection step of pressing, by air, the foamed mixed sand, contained in the mixing tank, so as to eject the foamed mixed sand; and a measurement step of measuring, once before or after the ejection step, an amount of the foamed mixed sand contained in the mixing tank. The material at least partially is not fed in the material feeding step in the cycle in which the amount of the foamed mixed sand is not less than a first threshold.

Advantageous Effects of Invention

According to an aspect of the present invention, it is possible to achieve (i) a molding method that makes it possible to reduce a cycle time that it takes to carry out a single cycle consisting of a process for forming a mold and (ii) a technique related to the molding method.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is front view of a molding machine of an embodiment in accordance with the present invention.

FIG. 2 is a cross-sectional view of the molding machine viewed along arrows A-A′ illustrated in FIG. 1.

FIG. 3 is perspective view illustrating a configuration of (i) a mixing tank of the molding machine illustrated in FIG. 1 and (ii) a vicinity of the mixing tank.

FIG. 4 is a cross-sectional view illustrating the configuration, illustrated in FIG. 3, of (i) the mixing tank of the molding machine and (ii) the vicinity of the mixing tank.

FIG. 5 is a cross-sectional view illustrating a state in which in the configuration, illustrated in FIG. 4, of (i) the mixing tank and (ii) the vicinity of the mixing tank, the mixing tank and a lid member are integral with each other by being connected by a connecting section.

FIG. 6 is a cross-sectional view illustrating a variable section provided in a circumferential surface of the lid member for sealing the mixing tank of the molding machine illustrated in FIG. 1.

FIG. 7 is a view schematically illustrating an example of a molding operation of the molding machine illustrated in FIG. 1.

FIG. 8 is a view schematically illustrating an example of the molding operation of the molding machine illustrated in FIG. 1.

FIG. 9 is a flowchart showing an example of a molding method carried out by the molding machine illustrated in FIG. 1.

FIG. 10 is a view schematically illustrating an example of the molding operation of the molding machine illustrated in FIG. 1.

FIG. 11 is a flowchart showing an example of the molding method carried out by the molding machine illustrated in FIG. 1.

FIG. 12 is a flowchart showing an example of a molding method carried out by a molding machine in accordance with a conventional technique.

FIG. 13 is a view illustrating a relationship between (a) the number of times of pre-ejection measurement and post-ejection measurement and (b) the weight of foamed mixed sand.

DESCRIPTION OF EMBODIMENTS Embodiment 1

The following description will discuss, with reference to FIGS. 1 to 11, a molding method in accordance with an embodiment of the present invention together with a molding machine used to carry out the molding method in accordance with an embodiment of the present invention.

(1) Overview of Molding Machine 1

FIG. 1 is front view illustrating an overall configuration of a molding machine 1 of Embodiment 1. FIG. 2 is a cross-sectional view illustrating a state of the molding machine 1 that has been cut along arrows A-A′ illustrated in FIG. 1. The molding machine 1 of Embodiment 1 can be used in a process for forming a mold by injecting a material into a cavity of a mold so as to fill the mold with the material. In particular, in a process for forming a core, foamed mixed sand obtainable by stirring a particulate aggregate, an aqueous binder, a surfactant can be suitably used as a material for a mold.

The molding machine 1 includes a mixing tank 2 having an ejection port. In the mixing tank 2, the molding machine 1 (i) produces foamed mixed sand with use of a stirring blade 51 (FIG. 2) and (ii) ejects the foamed mixed sand produced. The molding machine 1 ejects the foamed mixed sand, contained in the mixing tank 2, by pressing the foamed mixed sand by air supplied to an upper part inside the mixing tank 2. Thus, the molding machine 1 further includes a lid member 60 configured to open and close the mixing tank 2. The molding machine 1 further includes various driving systems so as to carry out operations of mixing to ejection.

As those driving systems, the molding machine 1 includes a vertically driving mechanism 3 and a connecting section 4. The vertically driving mechanism 3 is configured to vertically move the lid member 60 in a depth direction of the mixing tank 2. The connecting section 4 is capable of (i) connecting the mixing tank 2 and the lid member 60 to each other so as to integrate the mixing tank 2 and the lid member 60 with each other and (ii) disconnecting the mixing tank 2 and the lid member 60 from each other. In a case where the mixing tank 2 and the lid member 60 are integrated with each other by being connected by the connecting section 4, the vertically driving mechanism 3 vertically moves the mixing tank 2 together with the lid member 60. In contrast, in a case where the connecting section 4 does not connect the mixing tank 2 and the lid member 60 to each other, i.e., in a case where the mixing tank 2 and the lid member 60 are disconnected from each other, the vertically driving mechanism 3 vertically moves the lid member 60 without vertically moving the mixing tank 2. As described earlier, according to the molding machine 1, in a case where it is necessary to vertically move the mixing tank 2, it is possible to vertically move the mixing tank 2 with use of the vertically driving mechanism 3 by causing the connecting section 4 to connect the mixing tank 2 to the lid member 60. In other words, the molding machine 1 is configured to vertically move the mixing tank 2 by using the vertically driving mechanism 3 configured to vertically move the mixing tank 2 and the lid member 60. The molding machine 1 does not include any dedicated driving mechanism for vertically moving the mixing tank 2. Thus, the configuration of the molding machine 1 can be further simplified as compared with a configuration of a conventional molding machine including such a dedicated driving mechanism. This allows the molding machine 1 to have a simpler configuration. Furthermore, in a case where components each needed to be vertically moved are provided with respective dedicated driving mechanisms for vertical movement, it is made complicated to control, for example, a positional relationship between the driving mechanisms in which positional relationship the driving mechanisms drive the respective components. In contrast, according to Embodiment 1, the vertically driving mechanism 3 functions as both a driving mechanism for vertically moving the lid member 60 and a driving mechanism for vertically moving the mixing tank 2. This facilitates control.

(2) Details of Molding Machine 1

FIG. 3 is perspective view illustrating a configuration of (i) a mixing tank of the molding machine 1 of Embodiment 1 and (ii) a vicinity of the mixing tank. FIG. 4 is a cross-sectional view illustrating a state of the molding machine 1 that has been cut along arrows B-B′ illustrated in FIG. 3. As described earlier, the molding machine 1 includes the mixing tank 2, the lid member 60, a sealing air supply section 65 a (FIGS. 4 and 6), an ejection air supply section 65 b (FIG. 6), a pressing control section (not illustrated), the vertically driving mechanism 3, and the connecting section 4. The mixing tank 2 has at least one ejection port 20. The pressing control section (not illustrated) controls various functions of the lid member 60, the sealing air supply section 65 a, and the ejection air supply section 65 b. The molding machine 1 further includes a stirring mechanism 5 including the stirring blade 51 and a stirring shaft 53, a measurement section (not illustrated), a stopper mechanism 7 (FIG. 4), a material feeding section 8 (FIGS. 1 and 2), a driving mechanism 9 (FIGS. 1 and 2), and a mold 11 (FIG. 7).

Mixing Tank 2

The mixing tank 2 is a container for (i) mixing various materials so as to produce foamed mixed sand and (ii) storing therein the produced foamed mixed sand until the foamed mixed sand is ejected. The mixing tank 2 has (i) a lower part 21 provided with the at least one ejection port 20, (ii) an upper part 22 provided so as to face the lower part 21, and (iii) a lateral part 23 provided between the lower part 21 and the upper part 22, and is made of a transparent material. The lateral part 23 is a cylindrical structure. Since the cylindrical structure has a lower end side opening that is sealed by the lower part 21, the lower part 21 serves as a vessel bottom. This allows foamed mixed sand to be contained in the cylindrical structure. Furthermore, as illustrated in FIG. 3, the mixing tank 2 includes a plurality of struts 24 provided outside the lateral part 23 and configured to connect the lower part 21 and the upper part 22 to each other.

Lower Part 21

As illustrated in FIG. 4, the lower part 21 has a lower flange 25 and an ejection plate body 26. The lower flange 25 is shaped so as to laterally protrude from a vicinity of an outer diameter of the lateral part 23. The ejection plate body 26 is provided below the lower flange 25. The lower flange 25 is provided with an opening 25 a having a slightly larger diameter than the outer diameter of the lateral part 23. The lower flange 25 is connected to the lateral part 23 in a case where a lower end of the lateral part 23 is fitted to the opening 25 a. The ejection plate body 26 is connected to a lower surface of the lower flange 25. The ejection plate body 26 has an upper surface whose partial region is exposed toward the lateral part 23 at a location where the opening 25 a of the lower flange 25 is provided. Such an exposed part constitutes an upper surface of the vessel bottom of the mixing tank 2. The at least one ejection port 20 (described earlier) is a through hole provided in the ejection plate body 26. The at least one ejection port 20 includes three ejection ports 20 as illustrated in FIG. 3. Note, however, that the number of ejection ports 20 is not limited to three. As illustrated in FIG. 4, the ejection ports 20 can be provided with respective elastic plates 29 each for preventing a leakage of foamed mixed sand stored in the mixing tank 2. An elastic plate 29 can be, for example, a well-known valve structure (e.g., a rubber valve) provided with a slit.

The lower part 21 has a two-sheet structure as described above and thus can be made thick up to a certain point. This contributes to an improvement in rigidity of the mixing tank 2. The lower flange 25 and the ejection plate body 26 are preferably made of a material that is excellent in alkali resistance and mixed sand releasability. For example, the lower flange 25 and the ejection plate body 26 can be made of metal (e.g., stainless steel) or fluororesin (e.g., PTFE). In a case where the lower flange 25 and the ejection plate body 26 are made of metal, the mixing tank 2 can be more rigid. Note, however, that a material of which the lower flange 25 and the ejection plate body 26 are made is not limited to metal. Note also that the lower flange 25 and the ejection plate body 26 can be made of a single material or respective different materials.

Upper Part 22

As illustrated in FIGS. 3 and 4, the upper part 22 has an upper flange 27 shaped so as to laterally protrude from the vicinity of the outer diameter of the lateral part 23. As illustrated in FIG. 4, the upper flange 27 is provided with an opening 27 a having a slightly larger diameter than the outer diameter of the lateral part 23. The lower flange 27 is connected to the lateral part 23 in a case where an upper end of the lateral part 23 is fitted to the opening 27 a. The upper flange 27 can be made of metal (e.g., stainless steel) or fluororesin (e.g., PTFE). Note, however, that a material of the upper flange 27 is made is not limited to metal. The upper flange 27, which is thick up to a certain point, contributes to an improvement in rigidity of the mixing tank 2. Furthermore, in a case where the upper flange 27 is made of metal, the mixing tank 2 can be more rigid.

The upper part 22 further has clamping bushes 28 connected to an upper surface of the upper flange 27. The clamping bushes 28 are provided at respective two locations so as to face each other across a central shaft of the mixing tank 2. The clamping bushes 28 are each provided with a hole 28 a into which a corresponding one of clamping pins 43 (described later) is to be inserted. The clamping bushes 28, together with the clamping pins 43 (described later), constitute the connecting section 4. The clamping bushes 28 can be made of a material of which the upper flange 27 is made. Alternatively, the clamping bushes 28 can be made of a material different from the material of which the upper flange 27 is made.

Strut 24

The struts 24 are connected to the lower part 21 and the upper part 22 as illustrated in FIG. 3. As in the case of the lower part 21 and the upper part 22, the struts 24 are also preferably made of metal. With the configuration, the struts 24, together with the lower part 21 and the upper part 22, can contribute to an improvement in rigidity of the mixing tank 2. Furthermore, the struts 24 can contribute to maintenance of a distance, at which the lower part 21 and the upper part 22 are spaced, at a predetermined distance. According to Embodiment 1, four struts 24 in total are provided, at regular intervals, around an outer circumference of the lateral part 23. Note that the number of struts 24 provided around the outer circumference of the lateral part 23 is not limited to four.

Lateral Part 23

The lateral part 23 is fixed to the lower part 21 and the upper part 22, and constitutes a side surface part of a vessel for containing foamed mixed sand. The lateral part 23 is made of a transparent material. The lateral part 23 that is made of a transparent material makes it possible to satisfactorily observe a state of an inside of the mixing tank 2. Observation of the state of the inside of the mixing tank 2 makes it possible to not only determine a degree of mixing but also (i) determine whether there is any adhered matter that needs to be removed during cleaning of the mixing tank 2 and (ii) determine, during cleaning of the mixing tank 2, whether such an adhered matter remains. Furthermore, it is also possible to determine a state of sealing by a sealing body described later (e.g. inflation seal). The transparent material is selected from rigid plastics such as acrylic resin, polycarbonate, vinyl chloride, and polystyrene.

The lateral part 23 only needs to be strong enough to withstand (i) a weight of foamed mixed sand contained in the mixing tank 2 and (ii) a pressure applied to inject a material into a cavity of a mold so as to fill the mold with the material. As described earlier, rigidity of the mixing tank 2 can be achieved by the lower part 21 (described earlier), the upper part 22 (described earlier), and the struts 24 (described earlier). This allows the lateral part 23 to be relatively thin enough to withstand an internal pressure of the mixing tank 2.

Lid Member 60

The lid member 60 has a circumferential surface 60 a that faces an inner circumferential surface of an upper part 22 side opening of the mixing tank 2. The circumferential surface 60 a is provided with the sealing body 61.

The sealing body 61 can be deformed in a radiation direction (e.g., a radial direction) extending from a central part of the lid member 60 toward the circumferential surface 60 a. This allows the lid member 60 to have a larger diameter. Thus, in a case where the sealing body 61 is deformed in the radial direction, a tip of the sealing body 61 is brought into close contact with an inner circumferential surface of the mixing tank 2. This makes it possible to hermetically seal an opening provided in an upper part of the mixing tank 2. In other words, there is a gap between the circumferential surface 60 a of the lid member 60 and the inner circumferential surface of the mixing tank 2 before the sealing body 61 is deformed. The sealing body 61 is deformed by air that is sent under pressure, by the sealing air supply section 65 a, into a hollow part provided in the sealing body 61. In a case where the lid member 60 closes the opening provided in the upper part of opening of the mixing tank 2, the inside of the mixing tank 2 is hermetically sealed. In a case where the ejection air supply section 65 b sends air, under pressure, into the mixing tank 2, whose inside is hermetically sealed, foamed mixed sand contained in the mixing tank 2 is ejected via each of the ejection ports 20 by being pressed by air.

As illustrated in FIG. 4, the lid member 60 is provided with a stirring shaft insertion hole 64 having a bearing 68 in which the stirring shaft 53 is inserted, the stirring shaft 53 including the stirring blade 51 at a lower end thereof. A vertical movement of the lid member 60 and a vertical movement of the stirring shaft 53 and the stirring blade 51 are controlled so as to be integrally controlled by the vertically driving mechanism 3.

Sealing Air Supply Section 65 a

The sealing air supply section 65 a sends air, under pressure, to the hollow part (described earlier) of the sealing body 61. Specifically, the sealing air supply section 65 a is connect to an end of a flow path 62 provided in the lid member 60. In a step of ejecting, via each of the ejection ports 20, foamed mixed sand contained in the mixing tank 2, the sealing air supply section 65 a sends air, under pressure, to the hollow part (described earlier) so as to deform the sealing body 61. With the configuration, the upper end side opening of the mixing tank 2 is blocked, so that the inside of the mixing tank 2 is hermetically sealed.

Ejection Air Supply Section 65 b

The ejection air supply section 65 b supplies air into the mixing tank 2. Specifically, the ejection air supply section 65 b is connected to an introduction tube 67 provided in the lid member 60 illustrated in each of FIGS. 3 and 6. The ejection air supply section 65 b can supply air into the mixing tank 2 via the introduction tube 67. The ejection air supply section 65 b supplies air into the mixing tank 2 while the stopper mechanism 7 (described later) opens the ejection ports 20 of the mixing tank 2. In this case, the sealing air supply section 65 a hermetically seals the inside of the mixing tank 2 by inflating the sealing body 61 of the lid member 60. In a case where the ejection air supply section 65 b supplies air into the mixing tank 2 in this state, foamed mixed sand contained in the mixing tank 2 is ejected via each of the ejection ports 20. In short, the sealing air supply section 65 a and the ejection air supply section 65 b supply air at different timings. Note that the sealing air supply section 65 a supplies higher-pressure air than the ejection air supply section 65 b.

In order to supply air into the mixing tank 2, the ejection air supply section 65 b includes a port (not illustrated) and a pressure gauge (not illustrated) each provided in the lid member 60. To the port, a compressed air supply device is connected via a hose, a flowmeter, and a three-way valve. The compressed air supply device is configured to be capable of supplying compressed air into the mixing tank 2 via the flowmeter, the three-way valve, the hose, and the port. The pressure gauge measures a pressure within the mixing tank 2.

The ejection air supply section 65 b also includes an air supply control sections that is connected to each of the pressure gauge, the flowmeter, the three-way valve, and the compressed air supply device. The air supply control section controls respective operations of the compressed air supply device and the three-way valve.

Vertically Driving Mechanism 3

The vertically driving mechanism 3 is a mechanism configured to vertically move the lid member 60 in the depth direction of the mixing tank 2. The vertically driving mechanism 3 can vertically move the mixing tank 2 integrally with the lid member 60 as appropriate. Note that the vertically driving mechanism 3 constantly integrally vertically moves the lid member 60 and the stirring mechanism 5.

The vertically driving mechanism 3 includes (i) a cylinder 30 a and (ii) a rod 30 b each provided assuming that a vertical direction of the molding machine 1 is an axial direction, and (iii) an electric servomotor (not illustrated) for vertical driving. The rod 30 b has a lower end part that is connected to the lid member 60 via the connecting section 4. Furthermore, the lower end part of the rod 30 b is also connected to the stirring mechanism 5 via the connecting section 4. Thus, in a case where the electric servomotor is operated, the lid member 60 and the stirring mechanism 5 are configured to be integrally moved in (i) a direction in which the lid member 60 and the stirring mechanism 5 approach a bottom part of the mixing tank 2 and (ii) a direction opposite from the direction (i), i.e., in the vertical direction of the molding machine 1. The electric servomotor is connected to a vertical movement control section (not illustrated). The vertical movement control section controls operation of the electric servomotor so as to downwardly lower the lid member 60 and the stirring mechanism 5 while foamed mixed sand is being mixed in the mixing tank 2, and while the foamed mixed sand mixed is being ejected from the mixing tank 2. Then, the lid member 60 is placed at a location at which to close the opening provided in the upper part of the mixing tank 2, and the stirring blade 51 connected to a lower end part of the stirring mechanism 5 is placed at a location in the mixing tank 2 near the bottom part (FIG. 5). In contrast, while the mixing tank 2 is being weighed before or after mixing, and while a material of foamed mixed sand material is being introduced from the material feeding section (not illustrated) into the mixing tank 2, the vertical movement control section controls operation of the electric servomotor so that the lid member 60 is located above the opening provided in the upper part of the mixing tank 2 (FIG. 4).

Connecting Section 4

The connecting section 4 includes a vessel clamping mechanism 40 configured to connect and disconnect the vertically driving mechanism 3, the lid member 60 and the stirring mechanism 5, and the mixing tank 2 to/from each other. The vertically driving mechanism 3, the lid member 60 and the stirring mechanism 5, and the mixing tank 2 are connected to each other in a case where the clamping pins 43 of the vessel clamping mechanism 40 are inserted into respective holes 28 a of the clamping bushes 28 that are connected to the upper flange 27 of the upper part 22 of the mixing tank 2. Thus, the connecting section 4 is constituted by the vessel clamping mechanism 40 and the clamping bushes 28. The connecting section 4 has (i) an upper part to which the lower end part of the rod 30 b of the vertically driving mechanism 3 is connected and fixed and (ii) a lower part that is provided with at least one plate-like structure 4 a to which the lid member 60 is connected and fixed. As illustrated in FIGS. 1 and 2, the at least one plate-like structure 4 a includes plate-like structures 4 a provided at respective two locations so as to face each other across the stirring shaft 53 of the stirring mechanism 5. To each of the plate-like structures 4 a, the vessel clamping mechanism 40 is connected.

Vessel Clamping Mechanism 40

As illustrated in FIG. 4, the vessel clamping mechanism 40 includes a clamping cylinder 44 having a rod 41, at least one clamping base 42, and the clamping pins 43. The vessel clamping mechanism 40 pivotally supports the rod 41 of the plate-like structures 4 a that are fixed to the lid member 60. The rod 41 has a tip to which the at least one clamping base 42 is connected. The at least one base 42 is provided with a clamping pin 43 that is pivotally supported by a plate-like structure 4 a. The at least one clamping base 42 includes two clamping bases 42. The two clamping bases 42 are provided with respective two clamping pins 43 that are arranged in parallel to each other.

The clamping pins 43 each have a protruding end that is inserted into a corresponding one of the holes 28 a of the clamping bushes 28 that are connected to the upper flange 27 of the upper part 22 of the mixing tank 2 (described earlier). The clamping bushes 28 are provided at respective two locations in a circumferential direction of the upper flange 27 so as to correspond to the vessel clamping mechanism 40. The clamping bushes 28 are provided with respective two holes 28 a.

The clamping cylinder 44 can move the clamping base 42 via the rod 41. With the configuration, the clamping pins 43 that protrude from the clamping base 42 move forward or backward in a direction in which the clamping pins 43 protrude. This allows the clamping pins 43 to be inserted into or removed from the respective holes 28 a. The clamping cylinder 44 is controlled by a clamping control section (not illustrated) so as to insert/remove the clamping pins 43 into/from the respective holes 28 a. The connecting section 4 and the mixing tank 2 are connected to each other in a case where the clamping pins 43 are inserted into the respective holes 28 a. Such a state is, specifically, a state in which (i) the vertically driving mechanism 3 and the lid member 60 that are connected and fixed to the connecting section 4 and (ii) the mixing tank 2 are connected to each other. This allows not only the lid member 60 but also the mixing tank 2 to be vertically moved by the vertically driving mechanism 3.

Vessel Vertically Moving Cable Carrier 46

A vessel vertically moving cable carrier 46 illustrated in FIG. 2 has (i) one end that is connected and fixed to a frame F of the molding machine 1 and (ii) the other end that is connected and fixed to the connecting section 4. The vessel vertically moving cable carrier 46 supports and guides a cable provided in the molding machine 1. The vessel vertically moving cable carrier 46 lengthens and shortens the length of the vertical direction in accordance with the connecting section 4 that is vertically moved by operation of the vertically driving mechanism 3.

Stirring Mechanism 5

The stirring mechanism 5 mixes various materials fed into the mixing tank 2. As illustrated in FIG. 4, the stirring mechanism 5 includes the stirring blade 51, the stirring shaft 53, a mounting base 54, and a stirring motor 55. The stirring shaft 53 is provided in the vertical direction. The stirring blade 51 is provided at the lower end of the stirring shaft 53. The stirring motor 55 is connected to the stirring shaft 53. The stirring blade 51 is rotated by driving the stirring motor 55. Vertical movement of the stirring mechanism 5 in the vertical direction allows adjustment of the height of stirring blade 51 with respect to the mixing tank 2. The stirring mechanism 5 uses the stirring blade 51 to mix the various materials contained in the mixing tank 2. The various materials (e.g., a particulate aggregate, an aqueous binder, a surfactant, and water) are fed into the mixing tank 2 from, for example, the material feeding section 8 including feeding mechanisms configured to feed the respective various materials.

Note here that examples of the various materials include artificial sand (e.g. ESPEARL) serving as a particulate aggregate, sodium silicate serving as an aqueous binder, an anionic surfactant serving as a surfactant, and water. Note, however, that the various materials are not limited to the examples listed above, but can include, for example, other additive(s).

Stopper Mechanism 7

As illustrated in FIG. 4, the stopper mechanism 7 includes stoppers 7 a for blocking the respective ejection ports 20 of the lower part 21 of the mixing tank 2. The stoppers 7 a protrude upward from a stopper plate 7 b that is horizontally provided. The stopper mechanism 7 is configured to be moved by a mechanism (not illustrated) in a transverse direction of FIG. 4, i.e., in a horizontal direction.

The stopper mechanism 7 further includes a measurement section (not illustrated) configured to measure a weight of foamed mixed sand contained in the mixing tank 2.

Measurement Section

The measurement section is configured to measure a weight of foamed mixed sand contained in the mixing tank 2. The measurement section can be, for example, a load cell. For example, the measurement section can measure a weight of foamed mixed sand as below. Specifically, the measurement section (i) measures a weight of the mixing tank 2 in which the foamed mixed sand is stored while the lid member 60, the stirring blade 51, and the like are not in contact with the mixing tank 2, and (ii) deducts, from the measured weight, a weight of the mixing tank 2. Thus, the weight of the foamed mixed sand can be measured. The measurement section will be specifically described later.

Material Feeding Section 8

As illustrated in FIGS. 1 and 2, the material feeding section 8 feeds a material into the mixing tank 2 via an inlet (not illustrated) provided in the mixing tank 2.

According to Embodiment 1, the material feeding section 8 feeds, into the mixing tank 2, a material whose weight is greater than a weight needed to form a single mold. The material at least partially is not fed in a cycle in which an amount of foamed mixed sand is not less than a first threshold. Note here that the first threshold is (i) a value indicative of a weight that is great enough to make it unnecessary to additionally feed the material for subsequent ejection every time ejection is carried out and (ii) an upper limit up to which no foamed mixed sand overflows from inside the mixing tank 2 without fail. In the cycle in which the weight of the foamed mixed sand that remains in the mixing tank 2 after ejection is carried out is not less than the first threshold, the material feeding section 8 can omit the material feeding step without feeding any of the material, or can feed water to the mixing tank 2. In a case where the weight of the foamed mixed sand that remains in the mixing tank 2 after ejection is carried out is less than the first threshold, the material feeding section 8 feeds the material whose weight is greater than the weight needed to form a single mold. More specifically, immediately after ejection is carried out, the material feeding section 8 prepares, in advance, the material whose weight is necessary for subsequent ejection of foamed mixed sand. In a case where the weight of the foamed mixed sand that remains in the mixing tank 2 after ejection is carried out is not less than the first threshold, the material feeding section 8 omits feeding at least part of the material. In a case where the weight of the foamed mixed sand that remains in the mixing tank 2 after ejection is carried out is less than the first threshold, the material feeding section 8 feeds, into the mixing tank 2, the material in a determined amount described earlier, i.e., the material whose weight is greater than the weight needed to form a single mold.

This causes a weight of foamed mixed sand contained in the mixing tank 2 to be increased as molds are repeatedly formed. However, in a case where the weight is not less than the first threshold, the material at least partially is not fed into the mixing tank 2. As described earlier, in a case where it is unnecessary to additionally feed the material for subsequent ejection every time ejection is carried out, e.g., in a case where the weight of the foamed mixed sand that remains in the mixing tank 2 after ejection is carried out is not less than the first threshold, it is possible to prevent the material at least partially from being fed. Thus, in a case where the material feeding step is omitted, a time of the material feeding step can be set to 0 hour. In a case where water included in the material is fed, it is possible to reprepare foamed mixed sand by adjusting a water content in the mixing tank 2, while mixing the material for a shorter time. As described earlier, the material at least partially is not fed into the mixing tank 2 in a case where the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold. This allows the material to be mixed with use of the stirring blade 51 in the stirring mechanism 5 for a shorter time. The configuration allows a shorter cycle time as compared with a conventional technique in which (i) a weight of foamed mixed sand is measured twice before and after ejection every time a single cycle including the steps described earlier is carried out and (ii) a used amount of foamed mixed sand, which used amount is a difference value between weights obtained by the measurement carried out twice, is calculated so that a weight of a material for subsequent ejection is determined. The material feeding section 8 will be specifically described later.

Driving Mechanism 9

The driving mechanism 9 is configured to move the stopper mechanism 7 in the horizontal direction (e.g., in the transverse direction of FIG. 2). The driving mechanism 9 includes (i) a support guide part 91 (FIG. 1) configured to support a support part 7 d of the stopper mechanism 7 and a guide rod 92 of a stopper mechanism traveling cylinder (not illustrated). The driving mechanism 9 operates the stopper mechanism traveling cylinder so as to horizontally move a location of the stopper plate 7 b of the stopper mechanism 7. Specifically, the location of the stopper plate 7 b of the stopper mechanism 7 is moved between (i) a first location where the stoppers 7 a are located immediately below the ejection ports 20 of the mixing tank 2 and (ii) a second location where the stoppers 7 a are not located immediately below the ejection ports 20 of the mixing tank 2. The second location can be outside the molding machine 1. A location where the stoppers 7 a are not located immediately below the ejection ports 20 of the mixing tank 2 corresponds to a location to which the stoppers 7 a have been moved, so as not to prevent ejection, from a location immediately below the ejection ports 20 of the mixing tank 2 during a step of ejecting a foamed mixed product via each of the ejection ports 20 of the mixing tank 2 so as to inject the foamed mixed product into the mold 11.

The driving mechanism 9 also allows the mixing tank 2 to which the lid member 60 is not connected by the connecting section 4 to be horizontally moved while being placed on the stopper plate 7 b. The mixing tank 2 that is not connected to the lid member 60 is in a state in which the stoppers 7 a are fitted to the respective ejection ports 20. This makes it possible to stably place the mixing tank 2 on the stopper plate 7 b, so that the mixing tank 2 thus placed on the stopper plate 7 b can be moved from a location immediately below, for example, the lid member 60 and the stirring mechanism 5. In a case where it is possible to move a location of the mixing tank 2 as described above, it is possible to, for example, carry out a maintenance operation in which the mixing tank 2 is washed by being moved to outside the molding machine 1. A conventional molding machine includes a dedicated driving mechanism for horizontally moving the mixing tank 2. In contrast, the molding machine 1 of Embodiment 1 horizontally moves the mixing tank 2 with use of the driving mechanism configured to move the stopper mechanism 7 in the transverse direction of FIG. 2. Thus, the configuration of the molding machine 1 can be further simplified as compared with a configuration of a conventional molding machine. This allows the molding machine 1 to have a simpler configuration. Furthermore, in a case where components each needed to be moved in the transverse direction of FIG. 2 are provided with respective dedicated driving mechanisms, it is made complicated to control, for example, a positional relationship between the driving mechanisms in which positional relationship the driving mechanisms drive the respective components. In contrast, according to Embodiment 1, the driving mechanism 9 functions as both a driving mechanism for horizontally moving the stopper mechanism 7 and a driving mechanism for horizontally moving the mixing tank 2. This facilitates control. In addition, it is conventionally necessary to carry out maintenance with respect to a mixing tank by removing the mixing tank, which is weighty, from a molding machine within a limited space. This causes a deterioration in workability and requires a tremendous labor to carry out a cleaning operation with respect to the mixing tank. However, the configuration makes it possible to more conveniently carry out a maintenance operation with respect to a mixing tank as compared with a conventional configuration.

As illustrated in (iii) of FIG. 7, the mold 11 is a mold, provided on a lower side of the molding machine 1, for forming a mold by molding, into a predetermined shape, foamed mixed sand mixed by the stirring mechanism 5. The mold 11 is provided with an aperture 11 a to be filled. The aperture 11 a is provided adjacent to an ejection port 20 of the mixing tank 2 so as to be through the mold 11.

The molding machine 1 further includes a mold extruding mechanism (not illustrated) for taking out the mold from the mold 11 by opening the mold 11.

(3) Molding Operation Carried Out by Molding Machine 1

The following description will discuss, with reference to FIG. 7, a molding operation carried out by the molding machine 1 having the configuration described earlier. The following description will discuss operations that start to be carried out in a state in which foamed mixed sand is contained in advance in the mixing tank 2. Note that FIG. 7 does not illustrate foamed mixed sand for convenience.

Clamping Step

(i) of FIG. 7 illustrates how a clamping step is carried out, the clamping step being a step of carrying out a clamping operation at an original position. In the clamping step, the clamping pins 43 are inserted into the respective clamping bushes 28 of the upper part 22 first so that (i) the stirring mechanism 5 and the lid member 60 and (ii) the mixing tank 2 are connected to each other.

Opening Step

(ii) of FIG. 7 illustrates how an opening step is carried out, the opening step being a step of opening the ejection ports 20. In the opening step, the stoppers 7 a that block the respective ejection ports 20 are removed so that the ejection ports 20 are opened. Specifically, the stoppers 7 a are removed from the respective ejection ports 20 in a case where the lid member 60 and the mixing tank 2 that are connected to each other are lifted, in a zenith direction, to a location at a certain height at which location the stopper mechanism 7 travels. This state is illustrated in (ii) of FIG. 7. The state illustrated in (ii) of FIG. 7 allows the stopper mechanism 7 to be horizontally moved and evacuated from a location immediately below the mixing tank 2.

The example described earlier shows an aspect in which the mixing tank 2 that is in a clamped state is lifted and lowered by the vertically driving mechanism 3 so that the stoppers 7 a are inserted/removed into/from the respective ejection ports 20.

Ejection Step

(iii) FIG. 7 illustrates how an ejection step is carried out, the ejection step being a step of placing the mold 11 while the mixing tank 2 is in a clamped state, and pressing, by air, foamed mixed sand contained in the mixing tank 2, so as to eject the foamed mixed sand. In the ejection step, a mold placing step and an injection step are carried out. The mold placing step is a step of placing the mold 11. The injection step is a step of injecting foamed mixed sand into the mold 11 by supplying air into the mixing tank 2 that is closed by the lid member 60.

First, in the ejection step, a mold mechanism 10 moves the mold 11 to the location immediately below the mixing tank 2. Then, the vertically driving mechanism 3 downwardly lowers, to a location at which ejection is carried out, the mixing tank 2 that is integral with the stirring mechanism 5 and the lid member 60, so that the aperture 11 a to be filled of the mold 11 is provided adjacent to the ejection port 20 of mixing tank 2 (the mold placing step).

Before carrying out ejection, the molding machine 1 determines whether the sealing body 61 is suitably in close contact with the inner circumferential surface of the mixing tank 2, i.e., whether the opening of the mixing tank 2 is successfully hermetically sealed. Specifically, the molding machine 1 (i) measures a pressure of air that is supplied from the sealing air supply section 65 a to the sealing body 61 and (ii) determines whether a measured value is more than a threshold. The measured value that is not less than the threshold means that the sealing body 61 is suitably in close contact with the inner circumferential surface of the mixing tank 2. In contrast, the measured value that is less than the threshold means that, for example, air may leak from the sealing body 61. An error is indicated in a case where the measured value continues to be less than the threshold for a predetermined time from the start of supply of air. In this case, it is only necessary to carry out maintenance with respect to the sealing body 61, e.g., to inspect or exchange the sealing body 61.

In the injection step, air is supplied from the ejection air supply section 65 b into the mixing tank 2. Foamed mixed sand contained in the mixing tank 2 is pressed by the air thus supplied, so that a cavity of the mold 11 is filled with the foamed mixed sand via the ejection port 20 and the aperture 11 a to be filled. A time for which to fill the cavity with the foamed mixed sand is set in advance by a timer or the like. After the set time has elapsed, supply of air from the ejection air supply section 65 b is ended. The mold 11 is heated by heating means (not illustrated), and the foamed mixed sand with which the cavity is filled is heat-cured so that a mold is formed (a forming step). Then, the mold thus formed is taken out.

The ejection step is ended upon completion of the injection step. When the ejection step is ended, the mixing tank 2, the lid member 60, and the stirring mechanism 5 that are in the state illustrated in (iii) of FIG. 7 are integrally lifted again, in the zenith direction, to the location at which the stopper mechanism travels ((iv) of FIG. 7). Then, the stopper mechanism 7 moves to the location immediately below the mixing tank 2 and slightly lowers the mixing tank 2, the lid member 60, and the stirring mechanism 5 so as to insert the stoppers 7 a into the respective ejection ports 20 ((v) of FIG. 7). When the state of (v) of FIG. 7 is reached, the clamping pins 43 are removed from the respective holes 28 a of the clamping bushes 28 so that the mixing tank 2, the lid member 60, and the stirring mechanism 5 are disconnected from each other. During this period, the mold 11 is moved from the location immediately below the mixing tank 2. This ends a series of operations related to ejection. In the forming step, while the mold 11 is heated and foamed mixed sand is heat-cured, the mixing tank 2, the lid member 60, and the stirring mechanism 5 can be integrally lifted, in the zenith direction, to the location at which the stopper mechanism travels.

Measurement Step

(vi) of FIG. 7 illustrates how a measurement step of measuring a weight of foamed mixed sand contained in the mixing tank 2 is carried out after the ejection step and before the material feeding step illustrated in (vii) of FIG. 7. In (vi) of FIG. 7, since the mixing tank 2 that is in the state of (v) of FIG. 7 is unclamped, the lid member 60 does not seal the opening provided at the upper end of the mixing tank 2, so that the lid member 60 is located above the opening. The stirring blade 51 partially enters the mixing tank 2 via the opening provided at the upper end of the mixing tank 2. In this state, the stoppers 7 a of the stopper mechanism 7 block the respective ejection ports 20. Also in the material feeding step illustrated in (vii) of FIG. 7, the mixing tank 2 is unclamped. Thus, an operation carried out by the molding machine 1 in the measurement step overlaps with an operation carried out by the molding machine 1 in the material feeding step following the ejection step. This involves no waste. Thus, as described earlier, a further reduction in cycle time can be achieved by measuring, after the ejection step, the weight of the foamed mixed sand contained in the mixing tank 2.

In the measurement step, while a single cycle including (i) the material feeding step illustrated in (vii) of FIG. 7, (ii) the mixing step illustrated in (viii) of FIG. 7, and (iii) the ejection step (described earlier) is carried out, the measurement section provided in the stopper mechanism 7 measures, once, the weight of the foamed mixed sand contained in the mixing tank 2. The configuration further achieves a shorter cycle time as compared with a conventional technique in which a weight of foamed mixed sand is measured twice in a single cycle. As illustrated in (vi) of FIG. 7, a constituent member that is located above the mixing tank 2 including the lid member 60 and the stirring blade 51 is not in contact with the mixing tank 2. Thus, by (i) accurately measuring only a weight of the mixing tank 2 in which the foamed mixed sand is stored and (ii) deducting, from that weight, a weight of the mixing tank 2 which weight has been measured in advance, the measurement section can measure the weight of the foamed mixed sand contained in the mixing tank 2.

According to Embodiment 1, the molding machine 1 carries out the cycle (described earlier) in the following order: the ejection step illustrated in (iii) of FIG. 7, the measurement step in illustrated in (vi) of FIG. 7, and the material feeding step illustrated in (vii) of FIG. 7. That is, unless the material feeding step is omitted, the measurement section carries out the measurement step after the ejection step of the cycle (described earlier), i.e., carries out post-ejection measurement. Note here that, as described earlier, the connecting section 4 connects the mixing tank 2 and the lid member 60 to each other in the ejection step of ejecting the foamed mixed sand contained in the mixing tank 2. The connecting section 4 also disconnects the mixing tank 2 and the lid member 60 from each other in the material feeding step, the mixing step, and the measurement step. Thus, in a case where the measurement section carries out the measurement step after the ejection step, an operation carried out by the molding machine 1 after the ejection step and the operation carried out by the molding machine 1 in the measurement step can overlap with each other. This allows a further reduction in cycle time.

Note here that the molding machine 1 gives a warning such as an error indication and an alarm via a notification section (not illustrated) in a case where the weight of the foamed mixed sand which weight has been measured in the measurement step is less than a second threshold. Note here that the second threshold, which is a value indicative that the foamed mixed sand contained in the mixing tank 2 is insufficient, is a minimum value that allows the foamed mixed sand to be ejected from the mixing tank 2 without fail.

The configuration makes it possible to give a warning even if an abnormality (e.g., a leakage of the foamed mixed sand from each of the elastic plates 29 provided in the respective ejection ports 20 of the mixing tank 2) occurs and thus the foamed mixed sand contained in the mixing tank 2 is insufficient. This makes it possible to prevent continuance of a state in which the foamed mixed sand contained in the mixing tank 2 is insufficient.

An operator can carry out maintenance with respect to the molding machine 1 in a case where the warning (described earlier) is given (a maintenance step). For example, in a case where a gap between slits of an elastic plate 29 deteriorates and foamed mixed sand leaks from the gap, it is possible to carry out maintenance with respect to the molding machine 1 by exchanging the elastic plate 29 with a new elastic plate 29. Also in a case where the mixing tank 2 and the mold 11 are not suitably pressure-bonded together and foamed mixed sand is scattered over an upper surface of the mold 11, the operator can carry out maintenance to suitably pressure-bond the mixing tank 2 and the mold 11. By thus carrying out maintenance with respect to the molding machine 1, it is possible to normalize the molding machine 1.

As in Embodiment 1, in a case where post-ejection measurement is carried out and a weight needed to form a single mold is 2 kg, the second threshold is preferably not less than 4 kg and not more than 6 kg. That is, the second threshold is preferably not less than 200% and not more than 300% of the weight needed to form a single mold. The second threshold that is not less than 200% of the weight needed to form a single mold is not too low relative to the weight needed to form a single mold. Thus, as compared with a case where the second threshold is less than 200% of the weight needed to form a single mold, the configuration makes it possible to determine occurrence of the abnormality (described earlier) in a state in which the foamed mixed sand contained in the mixing tank 2 is not too insufficient. This makes it possible to more suitably prevent continuance of a state in which the foamed mixed sand contained in the mixing tank 2 is insufficient. The second threshold that is not more than 300% of the weight needed to form a single mold is not too high relative to the weight needed to form a single mold. This eliminates the need to, though the abnormality (described earlier) does not occur in the mixing tank 2, stop carrying out the steps, e.g., the material feeding step and the mixing step, each following the measurement step.

Note that the second threshold can be changed in accordance with a change in weight needed to form a single mold. As described earlier, the second threshold that is not less than 200% and not more than 300% of the weight needed to form a single mold falls within a preferable range. Thus, the second threshold can be set within a broad range.

In the example described earlier, the measurement section measures a weight of foamed mixed sand. However, according to Embodiment 1, the measurement section can use a level sensor to measure an amount different from the weight of foamed mixed sand, e.g., to measure a volume of foamed mixed sand in accordance with a height of the foamed mixed sand. That is, according to Embodiment 1, it is only necessary to carry out a cycle including a step based on an amount of foamed mixed sand.

Material Feeding Step

(vii) of FIG. 7 illustrates how the material feeding step of feeding, into the mixing tank 2, a material including a particulate aggregate, an aqueous binder, a surfactant, water, and the like is carried out.

In the material feeding step, as illustrated in (vii) of FIG. 7, while the mixing tank 2 is placed on the stopper plate 7 b, the lid member 60 and the stirring mechanism 5 are lifted to a location at which to feed the materials. In the material feeding step, the material including a particulate aggregate, an aqueous binder, a surfactant, water, and the like are fed into the mixing tank 2 in this state. The materials are fed, via the inlet provided in the mixing tank 2 or the opening provided in the upper part 22, from the material feeding section 8 illustrated in FIGS. 1 and 2. After the materials are fed, a weight of the mixing tank 2 into which the materials have been fed is measured so that an amount of the materials fed is controlled. The weight can be measured by the measurement section provided in the stopper mechanism 7. That is, at this stage, the mixing tank 2 is unclamped, and the vertically driving mechanism 3 is not in contact with the mixing tank 2 including the lid member 60 and the stirring blade 51. This makes it possible to accurately measure only the weight of the mixing tank 2 into which the materials have been fed.

Note here that foamed mixed sand is continuously ejected via each of the ejection ports 20 according to Embodiment 1. Thus, in the material feeding step of Embodiment 1, in a case where the weight of the foamed mixed sand contained in the mixing tank 2 is less than the first threshold, a material whose weight is greater than a weight needed to form a single mold is fed every time ejection is carried out. That is, according to Embodiment 1, after the mixing step illustrated in (viii) of FIG. 7 is carried out, the process returns to the state illustrated in (i) of FIG. 7, and then the cycle (described earlier) is repeatedly carried out and then. However, in the material feeding step of Embodiment 1, the material at least partially is not fed into the mixing tank 2 in a case where the weight of the foamed mixed sand that remains in the mixing tank 2 after ejection is not less than the first threshold. As described earlier, in a case where it is unnecessary to additionally feed the material for subsequent ejection every time ejection is carried out, e.g., in a case where the weight of the foamed mixed sand that remains in the mixing tank 2 after ejection is carried out is not less than the first threshold, the material at least partially is not fed. This makes it possible to prevent the material at least partially from being fed in the material feeding step. Since the material at least partially is not fed into the mixing tank 2, the material can be mixed with use of the stirring blade 51 in the stirring mechanism 5 for a shorter time. This allows a reduction in cycle time.

Assume that the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold. In this case, for example, the molding machine 1 receives, from the operator via an operation receiving section, an operation to select a material feeding time of 0. The molding machine 1 that has not received, from the operator via the operation receiving section, the operation to select a material feeding time of 0 feeds water into the mixing tank 2 while omitting feeding the material, excluding the water. The molding machine 1 that has received the operation to select a material feeding time of 0 omits carrying out the material feeding step, i.e., omitting feeding all the material.

According to Embodiment 1, the steps described earlier and the steps described below start to be carried out in a state in which foamed mixed sand is stored in advance in the mixing tank 2. In a case where post-ejection measurement is carried out and the weight needed to form a single mold is 2 kg, a weight of the foamed mixed sand stored in advance in the mixing tank 2 is preferably not less than 6 kg and not more than 12 kg. That is, the weight of the foamed mixed sand stored in advance in the mixing tank 2 is preferably not less than 300% and not more than 600% of the weight needed to form a single mold, i.e., a weight that allows molds to be formed not less than 3 times and not more than 6 times.

In a case where the weight of the foamed mixed sand stored in advance in the mixing tank 2 is not less than 300% of the weight needed to form a single mold, the weight of the foamed mixed sand stored in advance in the mixing tank 2 is not too light relative to the weight needed to form a single mold. Thus, as compared with a case where the weight of the foamed mixed sand stored in advance in the mixing tank 2 is less than 300% of the weight needed to form a single mold, the configuration makes it less likely for the weight of the foamed mixed sand contained in the mixing tank 2 to be less than the second threshold despite occurrence of an abnormality. As a result, the configuration makes it possible to more safely carry out the steps (described earlier) than the configuration in which the weight of the foamed mixed sand stored in advance in the mixing tank 2 is less than 300% of the weight needed to form a single mold. Furthermore, the configuration allows the first threshold to be reached in a shorter time, as compared with the configuration in which the weight of the foamed mixed sand stored in advance in the mixing tank 2 is less than 300% of the weight needed to form a single mold. Thus, it is possible to omit carrying out a step of feeding at least part of the material into the mixing tank 2. This allows a reduction in cycle time.

In a case where the weight of the foamed mixed sand stored in advance in the mixing tank 2 is not more than 600% of the weight needed to form a single mold, the weight of the foamed mixed sand stored in advance in the mixing tank 2 is not too heavy relative to the weight needed to form a single mold. Thus, as compared with a case where the weight of the foamed mixed sand stored in advance in the mixing tank 2 is more than 600% of the weight needed to form a single mold, the configuration can make it less likely for the foamed mixed sand to overflow from inside the mixing tank 2. Furthermore, as compared with the case where the weight of the foamed mixed sand stored in advance in the mixing tank 2 is more than 600% of the weight needed to form a single mold, the configuration makes it possible to achieve a shorter mixing time in the mixing step. As a result, as compared with the case where the weight of the foamed mixed sand stored in advance in the mixing tank 2 is more than 600% of the weight needed to form a single mold, the configuration makes it possible to achieve a shorter cycle time in the cycle including the mixing step.

Note that the weight of the foamed mixed sand stored in advance in the mixing tank 2 can be changed in accordance with a change in weight needed to form a single mold. As described earlier, in a case where the weight of the foamed mixed sand stored in advance in the mixing tank 2 is not less than 300% and not more than 600% of the weight needed to form a single mold, the weight of the foamed mixed sand stored in advance in the mixing tank 2 falls within a preferable range and thus can be set within a broad range.

As in Embodiment 1, in a case where post-ejection measurement is carried out and the weight needed to form a single mold is 2 kg, the first threshold is preferably not less than 8 kg and not more than 10 kg. That is, the first threshold is preferably not less than 400% and not more than 500% of the weight needed to form a single mold.

The first threshold that is not less than 400% of the weight needed to form a single mold is not too low relative to the weight needed to form a single mold. Thus, as compared with a case where the first threshold is less than 400% of the weight needed to form a single mold, the configuration makes it less likely for the weight of the foamed mixed sand contained in the mixing tank 2 to be less than the weight needed to form a single mold despite occurrence of an abnormality such as a leakage of foamed mixed sand via each of the ejection ports 20. As a result, as compared with the case where the first threshold is less than 400% of the weight needed to form a single mold, the configuration makes it possible to more reliably carry out the cycle including the steps (described earlier). The first threshold that is not more than 500% of the weight needed to form a single mold is not too high relative to the weight needed to form a single mold. Thus, as compared with a case where the first threshold is more than 500% of the weight needed to form a single mold, the configuration can make it less likely for the foamed mixed sand to overflow from inside the mixing tank 2. Furthermore, with the configuration, it does not take too long for the weight of the foamed the mixed sand contained in the mixing tank 2 to be not less than the first threshold. This suitably prevents the material at least partially from being fed in the material feeding step, so that a shorter cycle time can be achieved.

Note that the first threshold can be changed in accordance with a change in weight needed to form a single mold. As described earlier, the first threshold that is not less than 400% and not more than 500% of the weight needed to form a single mold falls within a preferable range. Thus, the second threshold can be set within a broad range.

As in Embodiment 1, in a case where post-ejection measurement is carried out and the weight needed to form a single mold is 2 kg, a weight of the material that is fed into the mixing tank 2 is preferably not less than 2.1 kg and not more than 4 kg. That is, the weight of the material that is fed into the mixing tank 2 is preferably not less than 105% and not more than 200% of the weight needed to form a single mold.

In a case where the weight of the material that is fed into the mixing tank 2 is not less than 105%, the weight of the material that is fed into the mixing tank 2 is not too light relative to the weight needed to form a single mold. With the configuration, it does not take too long for the weight of the foamed mixed sand contained in the mixing tank 2 to be not less than the first threshold. This suitably prevents the material at least partially from being fed in the material feeding step, so that a shorter cycle time can be achieved. Furthermore, in a case where the weight of the material that is fed into the mixing tank 2 is not more than 200% of the weight needed to form a single mold, the weight of the material that is fed into the mixing tank 2 is not too heavy relative to the weight needed to form a single mold. Thus, as compared with a case where the weight of the material that is fed into the mixing tank 2 is more than 200% of the weight needed to form a single mold, the configuration can make it less likely for the foamed mixed sand to overflow from inside the mixing tank 2. Furthermore, as compared with the case where the weight of the material that is fed into the mixing tank 2 is more than 200% of the weight needed to form a single mold, the configuration makes it possible to achieve a shorter mixing time in the mixing step. As a result, as compared with the case where the weight of the material that is fed into the mixing tank 2 is more than 200% of the weight needed to form a single mold, the configuration makes it possible to achieve a shorter cycle time in the cycle including the mixing step.

Note that the weight of the material that is fed into the mixing tank 2 can be changed in accordance with a change in weight needed to form a single mold. As described earlier, in a case where the weight of the material that is fed into the mixing tank 2 is not less than 105% and not more than 200% of the weight needed to form a single mold, the weight of the material that is fed into the mixing tank 2 falls within a preferable range and thus can be set within a broad range.

Mixing Step

(viii) of FIG. 7 illustrates how the mixing step of mixing a material, fed into the mixing tank 2, so as to produce foamed mixed sand is carried out after the material feeding step.

In the mixing step, the lid member 60 and the stirring mechanism 5 are lowered toward the mixing tank 2. In the mixing step, a location of the lid member 60 and the stirring mechanism 5 relative to the mixing tank 2 is lower than a location at which the clamping pins 43 are inserted into the respective holes 28 a of the clamping bushes 28.

After mixing is finished, the clamping pins 43 are inserted into the respective holes 28 a of the clamping bushes 28 by lifting the lid member 60 and the stirring mechanism 5 to a location that is equal in height to the location at which the clamping pins 43 are inserted into the respective holes 28 a of the clamping bushes 28. This state is illustrated in (i) of FIG. 7.

The operations described above are a series of operations carried out by the molding machine 1. The operations described above are carried out in the following order: ejection, mold formation, measurement, material feeding, and mixing. This cycle can be repeatedly carried out. In a case where the cycle is stopped for the purpose of, for example, maintenance, the cycle is stopped in the state illustrated in (i) of FIG. 7.

Note here that, in the mixing step of Embodiment 1, in the cycle in which the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold, not only the material can be at least partially not fed in the mixing step, but also the mixing step does not need to be carried out. That is, in the cycle in which the weight of the foamed mixed sand that remains in the mixing tank 2 after ejection is carried out is not less than the first threshold, a time for which to carry out the material feeding step and the mixing step can be set to 0 hour, and the ejection step can be continuously carried out.

For example, in the cycle in which the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold, the molding machine 1 can receive, via the operation receiving section (not illustrated) from the operator, an operation to select a mixing time of 0 or an operation not to select a mixing time of 0. The molding machine 1 that has received, from the operator, the operation to select a mixing time of 0 neither needs to carry out the mixing step nor needs to cause the stirring blade 51 of the stirring mechanism 5 to stir the material contained in the mixing tank 2. The molding machine 1 that has not received the operation to select a mixing time of 0 can cause the stirring blade 51 to stir the material contained in the mixing tank 2. As described earlier, in a case where (i) the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold and (ii) the molding machine 1 receives the operation to select a mixing time of 0, the mixing step can be omitted, and the mixing time can be set to 0 hour. This allows a further reduction in cycle time. The molding machine 1 that has not received the operation to select a mixing time of 0 does not omit the mixing step but causes the stirring blade 51 to stir the material contained in the mixing tank 2. Also in this case, the material at least partially is not fed into the mixing tank 2. This allows a reduction in mixing time.

In a case where the ejection step is continuously carried out while the material feeding step and the mixing step are omitted, the vertically driving mechanism 3 whose state has been changed from a state obtained after the measurement step illustrated in (vi) of FIG. 7 had been carried out to the state illustrated in (i) of FIG. 7 repeatedly carries out the cycle (described earlier).

Maintenance Step

The operator can also carry out maintenance with respect to the molding machine 1 unless any warning (described earlier) is given. For example, in a case where maintenance is carried out after (viii) of FIG. 7, the cycle is stopped in the state illustrated in (i) of FIG. 7 as described earlier, the clamping pins 43 are removed from the respective holes 28 a of the clamping bushes 28 so that the mixing tank 2 is disconnected from the lid member 60 and the stirring mechanism 5. This causes the mixing tank 2 to be placed on the stopper plate 7 b of the stopper mechanism 7. In this state, the lid member 60 and the stirring mechanism 5 are lifted. Then, when a connection 52 at which the stirring shaft 53 and the stirring blade 51 are connected is lifted above the upper part 22 of the mixing tank 2 and a work space can be secured around the connection 52, lifting of the lid member 60 and the stirring mechanism 5 is stopped. This state is illustrated in (ix) of FIG. 8.

Next, in the state illustrated in (ix) of FIG. 8, the connection 52 is operated so that the stirring blade 51 is removed from the stirring shaft 53 and only the stirring blade 51 is contained in the mixing tank 2. This state is illustrated in (x) of FIG. 8. The mixing tank 2 in which the stirring blade 51 is contained is placed on the stopper plate 7 b. Thus, by horizontally moving the stopper plate 7 b on which the mixing tank 2 is placed, the mixing tank 2 is moved to a location where the mixing tank 2 is not located immediately below the connecting section 4 and other driving systems. With the configuration, maintenance such as washing of the mixing tank 2 and the stirring blade 51 can be carried out at the location to which the mixing tank 2 has been moved from a location where the mixing tank 2 was immediately below the connecting section 4. The configuration in which the stirring blade 51 is thus removed makes it unnecessary to lift the stirring blade 51, including a lower part thereof, above the upper part 22 of the mixing tank 2. This allows a range of vertical movement of the stirring mechanism 5 to be set to a short range. The configuration also allows the vertically driving mechanism 3 to be smaller in size.

(4) Molding Method Carried Out by Molding Machine 1

The following description will discuss, with reference to FIG. 9, a molding method carried out by the molding machine 1 in accordance with Embodiment 1. FIG. 9 is a flowchart showing an example of the molding method carried out by the molding machine 1 illustrated in FIG. 1. The following description will discuss a molding method that starts to be carried out in a state in which foamed mixed sand is contained in advance in the mixing tank 2.

In step S101, the ejection air supply section 65 b of the molding machine 1 presses, by air, foamed mixed sand, contained in the mixing tank 2 of the molding machine 1, so as to eject the foamed mixed sand via each of the ejection ports 20 (the ejection step).

In step S102, the cavity of the mold 11 of the molding machine 1 is filled with the foamed mixed sand having been ejected via each of the ejection ports 20, a mold is formed by heat-curing the foamed mixed sand, and the mold is taken out (the forming step).

In step S103, the measurement section of the stopper mechanism 7 of the molding machine 1 measures, after the ejection step in step S101, a weight of the foamed mixed sand contained in the mixing tank 2 (the measurement step). As illustrated in FIG. 9, the measurement section measures, once after the ejection step of the cycle including the steps illustrated in FIG. 7, the weight of the foamed mixed sand contained in the mixing tank 2.

In step S104, the measurement section determines whether the weight of the foamed mixed sand contained in the mixing tank 2 is less than a first threshold. In a case where the material feeding section 8 determines that the weight of the foamed mixed sand contained in the mixing tank 2 is less than the first threshold (YES in step S104), the process proceeds to step S105. Unless the material feeding section 8 determines that the weight of the foamed mixed sand contained in the mixing tank 2 is less than the first threshold (NO in step S104), i.e., in a case where the material feeding section 8 determines that the weight of the foamed mixed sand contained in the mixing tank is not less than the first threshold, the process proceeds to step S108.

In step S105, the measurement section determines whether the weight of the foamed mixed sand contained in the mixing tank 2, the weight having been measured in the measurement step in step S103, is not less than a second threshold. In a case where the measurement section determines that the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the second threshold (YES in step S105), the process proceeds to step S106. In a case where the measurement section determines that the weight of the foamed mixed sand contained in the mixing tank 2 is less than the second threshold (NO in step S105), the process proceeds to step S111.

In step S106, the material feeding section 8 feeds a material whose amount is larger than an amount needed to form a single mold (the material feeding step).

In step S107, the material contained in the mixing tank 2 is mixed by being stirred by the stirring blade 51 of the stirring mechanism 5 of the molding machine 1, so that foamed mixed sand is produced (the mixing step). After step S107 is ended, the process returns to step S101, and the molding machine 1 repeatedly carries out the cycle including the steps described earlier.

In step S108, in a case where the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold, the molding machine 1 determines whether to feed water for adjusting a water content, i.e., whether to omit the material feeding step. For example, the molding machine 1 that has not received, from an operator via an operation receiving section, an operation to select a material feeding time of 0 determines that water will be fed (YES in step S108), and the process proceeds to step S109. In a case where the molding machine 1 has received, from the operator via the operation receiving section, the operation to select a material feeding time of 0, step S109 is omitted, and the process proceeds to step S110.

In step S109, the molding machine 1 feeds water into the mixing tank 2 while omitting feeding the material, excluding the water.

In step S110, in a case where the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold, the molding machine 1 determines whether to mix the material contained in the mixing tank 2, i.e., whether to select a mixing time of 0. For example, the molding machine 1 that has not received, from the operator via the operation receiving section, an operation to select a mixing time of 0 determines that the material contained in the mixing tank 2 will be mixed (YES in step S110). In this case, the molding machine 1 omits only feeding of at least part of the material in the material feeding step in step S106, and the process proceeds to step S107. The molding machine 1 that has received, from the operator via the operation receiving section, the operation to select a mixing time of 0 determines that the material contained in the mixing tank 2 will not be mixed (NO in step S110). In this case, the molding machine 1 omits not only feeding of at least part of the material in the material feeding step in step S106 but also the mixing step in step S107. In a case where step S107 is omitted, the process returns to step S101, and the molding machine 1 repeatedly carries out the cycle including the steps described earlier.

In step S111, in a case where the weight of the foamed mixed sand is less than the second threshold, the molding machine 1 causes a notification section thereof to give a warning. Here, in the cycle in which the weight of the foamed mixed sand is less than the second threshold, the molding machine 1 omits (i) feeding of at least part of the material in the material feeding step in step S106 and (ii) the mixing step in step S107, and gives the warning.

In step S112, after the warning is given in step S111, the operator carries out maintenance with respect to the molding machine 1 and finishes carrying out the steps.

Variation

The present invention is not limited to the embodiment described above, and may be altered in various ways by a skilled person within the scope of the claims. For example, according to Embodiment 1, the molding machine 1 carries out the measurement step after the ejection step. Alternatively, the molding machine 1 can carry out the ejection step after the measurement step. That is, pre-ejection measurement can be carried out instead of post-ejection measurement.

(5) Molding Operation Carried Out by Molding Machine 1

The following description will discuss, with reference to FIG. 10, a molding operation carried out by a molding machine 1 in accordance with a variation. FIG. 10 is a view schematically illustrating an example of the molding operation of the molding machine illustrated in FIG. 1. While omitting illustration of foamed mixed sand as in the case of FIG. 7, the following description will discuss operations that start to be carried out in a state in which foamed mixed sand is contained in advance in a mixing tank 2. Note that the following description will not discuss operations that are included in the operations illustrated in FIG. 10 and are similar to the operations illustrated in FIG. 7.

As in the case of (i) of FIG. 7, (i) of FIG. 10 illustrates how a clamping step is carried out, the clamping step being a step of carrying out a clamping operation at an original position.

(ii) of FIG. 10 illustrates how a measurement step of measuring a weight of the foamed mixed sand contained in the mixing tank 2 is carried out before an ejection step is carried out. In (ii) of FIG. 10, unlike the opening step, illustrated in (ii) FIG. 7, of opening the ejection ports 20 while the mixed tank 2 is in a clamped state, clamping carried out in the clamping step illustrated in (i) of FIG. 10 is released so that the measurement step is carried out.

In a case where the weight of the foamed mixed sand which weight has been measured in the measurement step illustrated in (ii) of FIG. 10 is less than a second threshold, the molding machine 1 carries out an operation similar to the operation carried out in (vi) of FIG. 7. Note, however, that, as compared with the second threshold described in Embodiment 1, in which post-ejection measurement is carried out, the second threshold described in the variation, in which pre-ejection measurement is carried out, is theoretically higher in weight needed to form a single mold and being a weight of foamed mixed sand ejected, i.e., an ejection amount. Thus, in a case where, as in the variation, pre-ejection measurement is carried out and a weight needed to form a single mold is 2 kg, the second threshold is preferably a weight of not less than 6 kg and not more than 8 kg, which weight is obtained by adding the ejection amount to the second threshold of Embodiment 1. That is, the second threshold is preferably not less than 300% and not more than 400% of the weight needed to form a single mold. The configuration also makes it possible to give a warning in a case where the weight of the foamed mixed sand is less than the second threshold even if an abnormality (e.g., a leakage of the foamed mixed sand from each of elastic plates provided in the respective ejection ports 20 of the mixing tank 2) occurs and thus the foamed mixed sand contained in the mixing tank 2 is insufficient. This makes it possible to prevent continuance of a state in which the foamed mixed sand contained in the mixing tank 2 is insufficient. Furthermore, by carrying out maintenance with respect to the molding machine 1, it is possible to normalize the molding machine 1.

(iii) of FIG. 10 illustrates how an opening step is carried out, the opening step being a step of opening the ejection ports 20 while the mixing tank 2 is in a clamped state. Note here that in the opening step illustrated in (iii) of FIG. 10, unlike the opening step illustrated in (ii) of FIG. 7, the mixing tank 2 that has been subjected to the measurement step illustrated in (ii) of FIG. 10 is clamped again so that the opening step is carried out.

As described earlier, in a case where pre-ejection measurement is carried out, an operation carried out by the molding machine 1 after the ejection step and an operation carried out by the molding machine 1 in the measurement step do not overlap with each other. In contrast, in a case where the cycle is carried out in the order of the ejection step, the measurement step, and the material feeding step as in Embodiment 1, the operation carried out by the molding machine 1 after the ejection step and the operation carried out by the molding machine 1 in the measurement step overlap with each other. Thus, the configuration in which post-ejection measurement is carried out causes no waste to the operations of the molding machine 1 as compared with the configuration in which pre-ejection measurement is carried out. This allows the configuration in which post-ejection measurement is carried out to achieve a further reduction in cycle time than the configuration in which pre-ejection measurement is carried out.

As in the case of (iii) FIG. 7, (iv) of FIG. 10 illustrates how the ejection step is carried out, the ejection step being a step of placing a mold 11 while the mixing tank 2 is in a clamped state, and pressing, by air, the foamed mixed sand contained in the mixing tank 2, so as to eject the foamed mixed sand.

As in the case of (iv) of FIG. 7, (v) of FIG. 10 illustrates how the mixing tank 2 that is in a clamped state, the lid member 60, and the stirring mechanism 5 are integrally lifted again, in a zenith direction, to a location at which a stopper mechanism travels.

As in the case of (v) FIG. 7, (vi) of FIG. 10 illustrates how a stopper mechanism 7 is moved to the original position, which is a location immediately below the mixing tank 2 that is in a clamped state, and stoppers 7 a are inserted into the respective ejection ports 20.

As in the case of (vii) of FIG. 7, (vii) of FIG. 10 illustrates how a material feeding step of feeding, into the mixing tank 2 that is in an unclamped state, a material including a particulate aggregate, an aqueous binder, a surfactant, water, and the like is carried out.

Note here that in the material feeding step illustrated in (vii) of FIG. 10, in a case where the weight of the foamed mixed sand contained in the mixing tank 2 is less than the first threshold, a material whose amount is larger than an amount needed to form a single mold is fed as in the case of (vii) of FIG. 7. Note also that in the material feeding step illustrated in (vii) of FIG. 10, no material is fed into the mixing tank 2 as in the case of (vii) of FIG. 7 in a case where the weight of the foamed mixed sand that remains in the mixing tank 2 after ejection is not less than the first threshold. Note, however, that the first threshold described in the variation, in which pre-ejection measurement is carried out, is theoretically higher, by an ejection amount, than the second threshold described in Embodiment 1, in which post-ejection measurement is carried out. Thus, in a case where, as in the variation, pre-ejection measurement is carried out and a weight needed to form a single mold is 2 kg, the first threshold is preferably a weight of not less than 10 kg and not more than 12 kg, which weight is obtained by adding the ejection amount to the first threshold of Embodiment 1. That is, the first threshold is preferably not less than 500% and not more than 600% of the weight needed to form a single mold. The configuration also allows a reduction in cycle time because no material is fed in a case where the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold.

As in the case of (viii) of FIG. 7, (viii) of FIG. 10 illustrates how the mixing step of mixing a material, fed into the mixing tank 2, so as to produce foamed mixed sand is carried out after the measurement step and the material feeding step.

In the mixing step illustrated in (viii) of FIG. 10, as in the case of (viii) of FIG. 7, in a case where the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold, the material feeding step is omitted and no material is mixed. That is, in a case where the weight of the foamed mixed sand contained in the mixing tank 2 is not less than the first threshold and an operation to select a mixing time of 0 has been received, a time for which to carry out the material feeding step and the mixing step is set to 0 hour by omitting the material feeding step and the mixing step, and the ejection step can be continuously carried out. The configuration of the mixing step illustrated in (viii) of FIG. 10 also allows a reduction in cycle time as in the case of (viii) of FIG. 7.

After mixing is finished, the process returns to a state illustrated in (i) of FIG. 10 and similar to (i) of FIG. 7. The operations described above are a series of operations carried out by the molding machine 1 in accordance with the variation. The operations described above are carried out in the following order: measurement, ejection, mold formation, material feeding, and mixing. This cycle can be repeatedly carried out. In a case where the cycle is stopped for the purpose of, for example, maintenance, the cycle is stopped in the state illustrated in (i) of FIG. 10. Maintenance can be carried out as in the case of (ix) and (x) of FIG. 8.

(6) Molding Method Carried Out by Molding Machine 1

The following description will discuss, with reference to FIG. 11, a molding method carried out by the molding machine 1 in accordance with the variation. FIG. 11 is a flowchart showing an example of the molding method carried out by the molding machine illustrated in FIG. 1. As in the case of FIG. 9, the following description will also discuss a molding method that starts to be carried out in a state in which foamed mixed sand is contained in advance in the mixing tank 2.

In step S201, the measurement section of the stopper mechanism 7 of the molding machine 1 measures, before the ejection step in step S202, a weight of the foamed mixed sand contained in the mixing tank 2 (the measurement step).

In step S202, after the measurement step in step S201, the ejection air supply section 65 b of the molding machine 1 presses, by air, the foamed mixed sand, contained in the mixing tank 2 of the molding machine 1, so as to eject the foamed mixed sand via each of the ejection ports 20 (the ejection step).

Steps S203 to S212 illustrated in FIG. 11 are identical to the respective corresponding steps of Embodiment 1 except that the first threshold and the second threshold are higher than the first threshold and the second threshold, respectively, of Embodiment 1 in proportion to an ejection amount. Thus, a description of steps S203 to S212 is omitted here.

EXAMPLES

The following description will discuss an example of a molding machine. Tests 1 to 3 were carried out under respective conditions shown below.

Test 1

In a test 1, LYTECORE (model number: LYTX, manufactured by SINTOKOGIO, LTD.) was used as a molding machine. Specifically, as in the case of Embodiment 1 and the variation, the molding machine used in the test 1 is a molding machine including a mixing tank including ejection ports, a stirring mechanism including a stirring blade, a pressing member, a stopper mechanism, and a mold.

Furthermore, in the test 1, a material including an aggregate, an aqueous binder, a surfactant, water, and the like was foamed and mixed in advance in the mixing tank in a state in which stoppers were inserted in the respective ejection ports of the mixing tank. In this way, in the test 1, foamed mixed sand having a weight of 8 kg, which is a weight needed to form four molds, was produced in advance.

The following description will discuss, with reference to FIG. 12, operations that start to be carried out in the state (described earlier) by the molding machine in the test 1 (Comparative Example 1). FIG. 12 is a flowchart showing an example of a molding method carried out by a molding machine in accordance with a conventional technique.

First, in the test 1, a weight of foamed mixed sand contained in the mixing tank was measured before ejection, i.e., before the ejection step was carried out (the measurement step) (see step S301 of FIG. 12). That is, pre-ejection measurement was carried out in the test 1.

Next, in the test 1, the stoppers were removed from the mixing tank, and the foamed mixed sand contained in the mixing tank was ejected by being pressed by air, so that the mold was filled with the foamed mixed sand (the ejection step) (see step 302 of FIG. 12).

Subsequently, in the test 1, the foamed mixed sand having been injected into the mold was heated for a certain period of time in the mold having a temperature of not less than 150° C. and not more than 350° C., so that a mold was formed (the forming step) (see step S303 of FIG. 12). The mold was taken out from the mold after a dehydration condensation reaction of the aqueous binder was finished.

Then, in the test 1, the weight of the foamed mixed sand contained in the mixing tank was measured after ejection, i.e., after the ejection step was carried out (the measurement step) (see step S304 of FIG. 12). That is, post-ejection measurement was carried out in the test 1.

Next, in the test 1, from the respective weights of the foamed mixed sand contained in the mixing tank, the weights having been measured before ejection in step S301 and after ejection in S304, respectively, a difference value between these weights were calculated. Subsequently, in the test 1, an ejection amount, which is a weight of foamed mixed sand ejected, was calculated from the difference value (see step S305 of FIG. 12).

Then, in the test 1, the material whose amount corresponds to the ejection amount calculated in step S305 was fed into the mixing tank (the material feeding step) (see step S306 of FIG. 12).

Next, in the test 1, the material contained in the mixing tank was mixed (the mixing step) (see step S307 of FIG. 12).

In the test 1, after step S307, the molding machine automatically repeatedly carried out a cycle including the steps described earlier, and a cycle time that it had taken to carry out a single cycle including the steps described earlier was measured.

As a result of the test 1, the cycle time that it had taken to carry out a single cycle including the steps described earlier was 150 seconds.

Test 2

In a test 2 (Example 1), a molding machine similar to the molding machine described earlier was used to carry out a molding method similar to the molding method shown in FIG. 11.

Furthermore, in the test 2, as in the case of the test 1, a material similar to the material described earlier was foamed and mixed in advance in a mixing tank in a state in which stoppers were inserted in respective ejection ports of the mixing tank. In this way, also in the test 2, foamed mixed sand having a weight of 8 kg, which is a weight needed to form four molds, was produced in advance.

The following description will discuss, with reference to FIG. 11, operations that start to be carried out in the state (described earlier) by the molding machine in the test 2.

Then, in the test 2, a weight of the foamed mixed sand contained in the mixing tank was measured before ejection, i.e., before the ejection step was carried out (the measurement step) (see step S201 of FIG. 11). That is, pre-ejection measurement was carried out in the test 2.

Next, in the test 2, the stoppers were removed from the mixing tank, and the foamed mixed sand contained in the mixing tank was ejected by being pressed by air, so that a mold was filled with the foamed mixed sand (the ejection step) (see step 202 of FIG. 11).

Subsequently, in the test 2, the foamed mixed sand having been injected into the mold was heated for a certain period of time in the mold having a temperature of not less than 150° C. and not more than 350° C., so that a mold was formed (the forming step) (see step S203 of FIG. 11). The mold was taken out from the mold after a dehydration condensation reaction of the aqueous binder was finished.

Then, in the test 2, after ejection, i.e., after the stoppers were inserted in the respective ejection ports after the ejection step was carried out, it was determined whether the weight of the foamed mixed sand contained in the mixing tank was less than 10 kg, which is a first threshold (see step S204 of FIG. 11). Furthermore, in the test 2, an aggregate having a weight of 2.2 kg heavier than 2 kg, which is a weight needed to form a single mold, was fed into the mixing tank in a cycle in which the weight of the foamed mixed sand was less than the first threshold. In addition to the aggregate, the material including an aqueous binder, a surfactant, and water was fed into the mixing tank (the material feeding step).

Moreover, in the test 2, in the cycle in which the weight of the foamed mixed sand was more than the first threshold, water for adjusting a water content was fed into the mixing tank while the material, excluding the water was not fed in the material feeding step, so that foamed mixed sand was reprepared.

In addition, the test 2 was carried out under the condition that, in the cycle in which the weight of the foamed mixed sand was less than 7 kg, which is a second threshold, the material feeding step and the mixing step were omitted, a warning was given, and maintenance was carried out with respect to the molding machine 1. That is, the test 2 was carried out under the condition that, in the cycle in which the weight of the foamed mixed sand was less than the second threshold, equipment of the molding machine 1 was stopped, a warning was issued, and then maintenance was carried out with respect to the molding machine 1.

Next, in the test 2, the material contained in the mixing tank was mixed (the mixing step) (see step S207 of FIG. 11).

In the test 2, after step S207, the molding machine automatically repeatedly carried out the cycle including the steps described earlier, and a cycle time, which is a time that it had taken to carry out a single cycle including the steps described earlier, was measured.

A result of the test 2 is shown in a view of FIG. 13, the view illustrating pre-ejection measurement. FIG. 13 is a view illustrating a relationship between (a) the number of times of pre-ejection measurement and post-ejection measurement and (b) the weight of the foamed mixed sand contained in the mixing tank 2. As illustrated in FIG. 13, in the test 2, there was not any abnormality such that the weight of the foamed mixed sand was less than the second threshold. Moreover, in the test 2, the cycle in which the weight of the foamed mixed sand was more than the first threshold appeared once out of 11 times measurement was carried out. In such a cycle, the material, excluding water was not fed in the material feeding step. As a result, at a time subsequent to the time when the material, excluding water was not fed in the material feeding step, the weight of the foamed mixed sand was reduced by 2 kg, which is a weight needed to form a single mold.

As a result of the test 2, the cycle time that it had taken to carry out a single cycle including the steps described earlier was 120 sec in the cycle in which the material was fed in the material feeding step. Note that the cycle time was 115 sec in the cycle in which the material, excluding water was not fed in the material feeding step.

As described earlier, in the test 2, also in the cycle in which the material, excluding water was fed in the material feeding step, the cycle time was successfully made approximately 20% shorter than the cycle time in the test 1. Note that the cycle time was successively further reduced in the cycle in which the material, excluding water was not fed in the material feeding step.

Test 3

Unlike the test 2 in which pre-ejection measurement was carried out, post-ejection measurement was carried out in a test 3 (Example 2). Specifically, in the test 3, the steps were carried out, as illustrated in FIG. 9, in the order of the ejection step, the forming step, the measurement step, the material feeding step, and the mixing step, not in the order of the measurement step, the ejection step, the forming step, the material feeding step, and the mixing step.

Moreover, in the test 3, in a cycle in which a weight of foamed mixed sand was more than 8 kg, which is a first threshold, water for adjusting a water content was fed into a mixing tank while a material, excluding the water was not fed in the material feeding step, so that foamed mixed sand was reprepared.

In addition, the test 3 was carried out under the condition that, in the cycle in which the weight of the foamed mixed sand was less than 5 kg, which is a second threshold, the material feeding step and the mixing step were omitted, a warning was given, and maintenance was carried out with respect to the molding machine 1.

Except for these points, in the test 3, the cycle including the steps described earlier was repeatedly carried out so that a cycle time was measured, as in the case of the test 2.

A result of the test 3 is shown in a view of FIG. 13, the view illustrating post-ejection measurement. As illustrated in FIG. 13, in the test 3, there was also not any abnormality such that the weight of the foamed mixed sand was less than the second threshold, as in the case of the test 2. Moreover, in the test 3, the cycle in which the weight of the foamed mixed sand was more than the first threshold also appeared once out of 11 times measurement was carried out, as in the case of the test 2. In such a cycle, the material, excluding water was not fed in the material feeding step. As a result, at a time subsequent to the time when the material, excluding water was not fed in the material feeding step, the weight of the foamed mixed sand was reduced by 2 kg, which is a weight needed to form a single mold.

As a result of the test 3, the cycle time that it had taken to carry out a single cycle including the steps described earlier was 110 sec in the cycle in which the material was fed in the material feeding step. Note that the cycle time was 105 sec in the cycle in which the material, excluding water was not fed in the material feeding step.

As described earlier, the test 3, in which post-ejection measurement had been carried out, allowed a further reduction in cycle time as compared with the test 2.

The present invention is not limited to the embodiment described above, and may be altered in various ways by a skilled person within the scope of the claims. Any embodiment derived from a proper combination of technical means disclosed is also encompassed in the technical scope of the present invention.

Aspects of the present invention can also be expressed as follows:

A molding method in accordance with an aspect of the present invention includes: repeatedly carrying out a cycle, the cycle including: a material feeding step of feeding, into a mixing tank, a material whose amount is larger than an amount that is needed to form a single mold; a mixing step of mixing the material, contained in the mixing tank, so as to produce foamed mixed sand; an ejection step of pressing, by air, the foamed mixed sand, contained in the mixing tank, so as to eject the foamed mixed sand; and a measurement step of measuring, once before or after the ejection step, an amount of the foamed mixed sand contained in the mixing tank. The material at least partially is not fed in the material feeding step in the cycle in which the amount of the foamed mixed sand is not less than a first threshold.

According to the configuration, the measurement step is carried out only once in a single cycle. Thus, the configuration allows a shorter cycle time as compared with a conventional technique in which the measurement step is carried out twice in a single cycle. Furthermore, according to the configuration, the amount of the foamed mixed sand contained in the mixing tank is increased as molds are repeatedly formed. Note, however, that the material at least partially is not fed in the material feeding step in a case where the amount of the foamed mixed sand is not less than the first threshold. As described earlier, in a case where it is unnecessary to additionally feed the material for subsequent ejection every time ejection is carried out, e.g., in a case where the amount of the foamed mixed sand that remains in the mixing tank after ejection is carried out is not less than the first threshold, it is possible to prevent the material at least partially from being fed in the material feeding step. Furthermore, by preventing the material at least partially from being fed in the material feeding step, the material at least partially is not fed into the mixing tank. This allows a reduction in mixing time in the mixing step. As a result, the configuration also allows a shorter cycle time as compared with a conventional technique in which (i) an amount of foamed mixed sand is measured twice in a single cycle before and after ejection and (ii) a difference value between amounts obtained by the measurement carried out twice is calculated so that an amount of the material for subsequent ejection is determined.

The molding method in accordance with an aspect of the present invention is configured such that the ejection step is carried out while the mixing tank and a lid member configured to open and close the mixing tank are connected to each other. The material feeding step, the mixing step, and the measurement step are carried out while the mixing tank and the lid member are disconnected from each other. The measurement step is preferably carried out before or after the ejection step.

According to the configuration, in a case where post-ejection measurement in which the amount of the foamed mixed sand is measured after the ejection step is carried out, an operation carried out by the molding machine after post-ejection measurement and an operation carried out by the molding machine in the measurement step can overlap with each other. This involves no waste in operation of the molding machine. Thus, in a case where post-ejection measurement is carried out in the configuration, it is possible to achieve a further reduction in cycle time.

The molding method in accordance with an aspect of the present invention is preferably configured such that the mixing step is further omitted in the cycle in which the amount of the foamed mixed sand is not less than the first threshold.

According to the configuration, the mixing time can be set to 0 hour in a case where the amount of the foamed mixed sand is not less than the first threshold. This makes it possible to achieve a further reduction in cycle time.

The molding method in accordance with an aspect of the present invention is preferably configured such that a weight of the material that is fed into the mixing tank in the material feeding step is not less than 105% and not more than 200% of a weight that is needed to form the single mold.

As in the configuration, in a case where the weight of the material that is fed into the mixing tank is not less than 105% of the weight needed to form the single mold, the weight of the material that is fed into the mixing tank 2 is not too light relative to the weight needed to form the single mold. With the configuration, it does not take too long for the weight of the foamed mixed sand contained in the mixing tank to be not less than the first threshold. This suitably prevents the material at least partially from being fed in the material feeding step, so that a shorter cycle time can be achieved. Furthermore, in a case where the weight of the material that is fed into the mixing tank is not more than 200% of the weight needed to form the single mold, the weight of the material that is fed into the mixing tank is not too heavy relative to the weight needed to form the single mold. Thus, as compared with a case where the weight of the material that is fed into the mixing tank is more than 200% of the weight needed to form the single mold, the configuration can make it less likely for the foamed mixed sand to overflow from inside the mixing tank. Furthermore, as compared with the case where the weight of the material that is fed into the mixing tank is more than 200% of the weight needed to form the single mold, the configuration makes it possible to achieve a shorter mixing time in the mixing step. As a result, as compared with the case where the weight of the material that is fed into the mixing tank is more than 200% of the weight needed to form the single mold, the configuration makes it possible to achieve a shorter cycle time in the cycle including the mixing step.

The molding method in accordance with an aspect of the present invention is preferably configured such that water included in the material is fed into the mixing tank in the material feeding step in the cycle in which the amount of the foamed mixed sand is not less than the first threshold.

According to the configuration, since water that makes it possible to adjust a water content is fed into the mixing tank, it is possible to reprepare foamed mixed sand by adjusting the water content in the mixing tank 2.

The molding method in accordance with an aspect of the present invention is preferably configured such that a warning is given in the cycle in which the amount of the foamed mixed sand is less than a second threshold.

The configuration makes it possible to give a warning even if an abnormality (e.g., a leakage of the foamed mixed sand from each of elastic plates provided in respective ejection ports of the mixing tank) occurs and thus the foamed mixed sand contained in the mixing tank is insufficient. This makes it possible to prevent continuance of a state in which the foamed mixed sand contained in the mixing tank is insufficient.

The molding method in accordance with an aspect of the present invention is preferably configured such that a molding machine for carrying out the cycle is subjected to maintenance in a case where the warning is given.

With the configuration, it is possible to normalize the molding machine by carrying out maintenance with respect to the molding machine in a case where an abnormality (e.g., a leakage of the foamed mixed sand from each of the elastic plates provided in the respective ejection ports of the mixing tank) occurs.

REFERENCE SIGNS LIST

-   1 Molding machine -   2 Mixing tank -   5 Stirring mechanism -   8 Material feeding section -   20 Ejection port -   51 Stirring blade -   60 Lid member -   65 b Ejection air supply section 

1. A molding method comprising: repeatedly carrying out a cycle, the cycle including: a material feeding step of feeding, into a mixing tank, a material whose amount is larger than an amount that is needed to form a single mold; a mixing step of mixing the material, contained in the mixing tank, so as to produce foamed mixed sand; an ejection step of pressing, by air, the foamed mixed sand, contained in the mixing tank, so as to eject the foamed mixed sand; and a measurement step of measuring, once before or after the ejection step, an amount of the foamed mixed sand contained in the mixing tank, the material at least partially not being fed in the material feeding step in the cycle in which the amount of the foamed mixed sand is not less than a first threshold.
 2. The molding method as set forth in claim 1, wherein the ejection step is carried out while the mixing tank and a lid member configured to open and close the mixing tank are connected to each other, and the material feeding step, the mixing step, and the measurement step are carried out while the mixing tank and the lid member are disconnected from each other, and the measurement step is carried out before or after the ejection step.
 3. The molding method as set forth in claim 1, wherein the mixing step is further omitted in the cycle in which the amount of the foamed mixed sand is not less than the first threshold.
 4. The molding method as set forth in claim 1, wherein a weight of the material that is fed into the mixing tank in the material feeding step is not less than 105% and not more than 200% of a weight that is needed to form the single mold.
 5. The molding method as set forth in claim 1, wherein water included in the material is fed into the mixing tank in the material feeding step in the cycle in which the amount of the foamed mixed sand is not less than the first threshold.
 6. The molding method as set forth in claim 1, wherein a warning is given in the cycle in which the amount of the foamed mixed sand is less than a second threshold.
 7. The molding method as set forth in claim 6, wherein a molding machine for carrying out the cycle is subjected to maintenance in a case where the warning is given. 